Resource post for January
About 80 million adult Americans suffer from at least one type of cardiovascular disorder. This is equivalent to 1 in every 3 adults. Diastolic dysfunction is a commonly used term nowadays in connection with diagnosis of heart disease. This term, however, is fairly new, and the dysfunction has only been identified with improved diagnostic techniques.
What is diastolic dysfunction?
Before we can understand this disorder, we first have to understand how our heart works.
“Lub-dub” This is the sound that our heart makes with each and every heartbeat. And with every beat, the heart contracts and relaxes. The contraction phase when the ventricles contract to pump blood out of the heart is called the systole. The relaxation phase when the ventricles relax and get filled with blood pumped from above by the atria is the called diastole. The “lub-dub” sound is actually made by the heart’s valves as they close and open during the contraction – relaxation cycle.
Our heart has 4 valves, namely:
- The tricuspid valve divides the right atrium from the right ventricle.
- The mitral valve divides the left atrium from the left ventricle.
- The pulmonary valve separates the right ventricle from the pulmonary artery, the big blood vessel that brings blood to the lungs.
- The aortic valve is separates the left ventricle from the aorta, the big artery that carries blood from the heart to the body.
The soft “lub” is the sound that the mitral and tricuspid valves make when they close at the start of the systole or contraction phase. The louder “dub” is the sound that the aortic and pulmonary valves make when they close at the start of the diastole or relaxation phase.
Diastolic dysfunction occurs when the relaxation or diastolic phase of the heart does not proceed normally. This has something to do with “stiff” heart muscles leading to the failure of the ventricle to relax normally. This inability of the ventricle to completely relax results in:
- the pressure in the ventricle to increase above normal.
- difficulty for the blood to enter the ventricle in the next heartbeat.
According to the American Heart Association (AHA), when not managed properly, diastolic dysfunction leads to inefficient pumping of the heart and “can cause increased pressure and fluid in the blood vessels of the lungs (pulmonary congestion). It can also cause increased pressure and fluid in the blood vessels coming back to the heart (systemic congestion).” This can eventually lead to diastolic heart failure.
According to this article in the American Academy of Family Physicians (AAFP) site
“diastolic heart failure is defined as a condition caused by increased resistance to the filling of one or both ventricles; this leads to symptoms of congestion from the inappropriate upward shift of the diastolic pressure-volume relation.”
A condition called systolic dysfunction also exists.
What causes diastolic dysfunction?
The disorder seems to be especially common in elderly women, even among those not previously diagnosed with heart disease. The following cardiovascular conditions can lead to the stiffening of the ventricles and thus diastolic dysfunction:
- aortic stenosis
- chronic hypertension
- coronary artery disease
- some forms of cardiomyopathy, e.g. hypertrophic and restrictive cardiomyopathy
How is diastolic dysfunction detected and diagnosed?
In its early stages, diastolic dysfunction does not manifest in obvious symptoms. Perhaps the earliest noticeable symptom would be dyspnea or shortness of breath. However, since this is a very common symptom for many kinds of diseases and disorders, diastolic dysfunction is often “missed” during routine medical check ups. Thus, “diastolic dysfunction may be present for several years before it is clinically evident.”
It its advanced stage, when diastolic dysfunction has progressed to the point of causing diastolic heart failure, the following symptoms and related conditions may be evident:
- Abnormal heart rhythms such as atrial fibrillation
- Periodic increase in blood pressure
- Decreased tolerance to physical exercise
- Severe breathlessness even without exertion
- Edema or accumulation of fluids in the feet and ankles
- Acute pulmonary congestion
A standard electrocardiogram or ECG unfortunately cannot easily distinguish between systolic and diastolic dysfunction. The most reliable but rather invasive diagnostic method is cardiac catheterization. As a less invasive alternative, a two-dimensional echocardiography with Doppler function can be used, although the physician must be well-trained in evaluating “the characteristics of diastolic transmitral and pulmonary venous flow pattern” in order to diagnose diastolic dysfunction.
How is diastolic dysfunction managed?
There is no easy way to treat diastolic dysfunction. However it can be effectively managed through treatment and management of the underlying conditions, namely:
High blood pressure. Management of hypertension is essential in the management of diastolic dysfunction. The AHA gives a comprehensive review of hypertension, including online tools to check for risk factors and blood pressure monitoring.
Coronary artery disease. CAD on its own requires aggressive management strategies to prevent heart attacks. This animation on the AHA site explains clearly how CAD develops.
Aortic valve stenosis. The aortic valve can also become stiff or is misformed at birth, resulting in aortic stenosis, a condition which puts a strain on the left ventricle. Usually, this condition is relieved by surgical interventions.
Arrhythmia. Abnormal heart rhythms such as atrial fibrillation need to be managed effectively to avoid further complications. The AHA site also gives a useful animation on atrial fibrillation. More information about arrhythmias can be found here.
Currently, there is a scarcity of conclusive data on therapies specifically for diastolic heart dysfunction and failure. However, the American College of Cardiology and the American Heart Association have jointly come up with guidelines which “recommend that physicians address blood pressure control, heart rate control, central blood volume reduction, and alleviation of myocardial ischemia when treating patients with diastolic heart failure. These guidelines target underlying causes and are likely to improve left ventricular function and optimize hemodynamics.” Medications used for the management of diastolic heart failure are summarized in this AAFP article (Table 4).
Can diastolic dysfunction be prevented?
Like many heart disorders, diastolic dysfunction and heart failure are preventable.
“Primary prevention of diastolic heart failure includes smoking cessation and aggressive control of hypertension, hypercholesterolemia, and coronary artery disease. Lifestyle modifications such as weight loss, smoking cessation, dietary changes, limiting alcohol intake, and exercise are equally effective in preventing diastolic and systolic heart failure.”
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